Conventionally, as a method of generating a color separation table for a process for separating a color signal into colors of color agents (inks) of a color printer (to be referred to as an ink color separation process hereinafter), method 1 which divides a color separation table defined by a cube into six tetrahedrons, further divides each tetrahedron into triangles, and obtains color separation amounts on a grid inside each triangle by an interpolation process from color separation tables of the three sides of the triangle has been proposed (Japanese Patent Laid-Open No. 2002-33930). This method 1 has proposed to calculate contour lines of ink amounts of the color separation tables of the three sides, and then obtaining color separation amounts inside the triangle. To do this, after linear contour lines are calculated, smooth table creation is implemented by a nonlinear curve approximation process.
However, in the conventional method, when the color separation tables of the three sides have complicated shapes, it is difficult to calculate linear contour lines from ink amounts of the color separation tables of the three sides. In some cases, solutions cannot be obtained. Furthermore, when a nonlinear interpolation process is to be implemented to improve inner grayscale characteristics, contour lines calculated in advance by a linear interpolation process must undergo a complicated process, i.e., nonlinear curve approximation.